The invention relates to a method of manufacturing plastic-bonded, anisotropic permanent magnets in which semi-manufactured articles formed from permanent magnetic particles of oxide material and having an easy axis of magnetization are mixed with a plastic binder and are subjected to a molding process in a magnetic orienting field.
It is known to manufacture plastic-bonded, anisotropic permanent magnets (plastoferrites), for example, by mixing barium hexaferrite (BaO.6Fe.sub.2 O.sub.3) or strontium hexa ferrite (SrO.6Fe.sub.2 O.sub.3), in the form of a semi-manufactured article such as aniso tropic, sintered intermediate members having cross-sections of 1 to 2 cm.sup.2 and lengths of 2-4 mm, with a plastic binder and subjecting the mixture to a molding process. The molding process may be, for example, an injection molding process in which the intermediate members are oriented by applying a magnetic field. A disadvantage of this method is that at comparatively high filling factors of magnetic material in plastic no optimum remanence values are obtained because the (coarse) intermediate members hinder each other when rotating under the influence of the magnetic field applied during the molding process.
However, when the filling factor of magnetic material in the plastic is chosen small enough such that the intermediate members can move freely, the filling factor becomes too small to enable the finished product to reach sufficient remanence values.